Both but as always it depends on context. I didn't sleep well (last night) or I haven't slept well (in days). In the first instance, the time marker forces the verb into the simple past. In the second, you are describing your present state. Using a time duration (such as 'in days') explains why you look tired now but doesn't force the verb into the past.

Hallo huda . My name is Rahma . Will you be my speaking partner ?

The both are right..if u r talking about yesterday then u can use did..but if u r talking about past week or month or year then u have to use have or has... I'm from uk.. I'm Muslim..if u wanna start our conversation we can..

Both are ok

I didn't slept well is correct